The urgency of removing organic contaminants from underground water formations has become increasingly more apparent during the last three decades. This urgency has spawned a tremendous effort to improve ground water decontamination techniques.
Subsurface decontamination techniques fall into one of two broad classes, above-ground methods and in situ methods. Above-ground methods generally require the removal of contaminated soil and water from the subsurface formation, treatment of such soil and water in above-ground facilities, and re-introduction of the decontaminated soil and water into the subsurface formation. Above-ground methods have been found to be effective but extremely expensive, especially where the subsurface contamination is wide-spread.
For this reason, in situ methods are preferred whenever possible. In in situ methods, the contaminated zone within the subsurface formation is treated in situ by heating or by some other process to mobilize the contaminants. Once mobilized, the contaminants, in the form of contaminated liquids and vapors, are withdrawn from a contaminated zone via one or more extraction wells. The contaminated liquids and vapors are thereafter treated separately at above ground facilities.
One problem with such in situ methods is how to properly control the treatment process so as to maximize yields while minimizing costs. For many prior art in situ methods, the treatment process has been controlled by reference to the amount of non-soluble liquid contaminants extracted from the subsurface formation. This is especially true for in situ methods where the predominant contaminants are non-volatile heavy organic materials. The applicants have discovered, however, that such prior art control methods are based on erroneous assumptions and can lead to marked inefficiencies in the remediation process.
Accordingly, there is a need for an improved subsurface remediation process having greater efficiency than processes of the prior art.